numerical instability

[Willi Braun]

Following model behaves numerical instable:

loadString("
model testCFExpr1
  Real x;
initial equation
  der(x) = 3.14159/2;
equation
  sin(der(x)) = cos(x);
end testCFExpr1;
");

simulate(testCFExpr1, stopTime=10, tolerance=1e-4);
val(x,0);
val(x,10);

val(der(x),0);
val(der(x),10);

simulate(testCFExpr1, stopTime=10, tolerance=1e-5);
val(x,0);
val(x,10);

val(der(x),0);
val(der(x),10);

simulate(testCFExpr1, stopTime=10, tolerance=1e-6);
val(x,0);
val(x,10);

val(der(x),0);
val(der(x),10);

simulate(testCFExpr1, stopTime=10, tolerance=1e-7);
val(x,0);
val(x,10);

val(der(x),0);
val(der(x),10);

simulate(testCFExpr1, stopTime=10, tolerance=1e-8);
val(x,0);
val(x,10);

val(der(x),0);
val(der(x),10);

results with different tolerances:

tolerance = 0.0001:
-0.000001326803844565571
1.5707084777514067
1.570795
0.00008784904348996832

tolerance = 0.00001:
-0.000001326803844565571
1.5707236871192907
1.570795
0.00007263967560595125

tolerance = 0.000001:
-0.000001326803844565571
526.3524099363941
1.570795
18.985196381642503

tolerance = 0.0000001:
-0.000001326803844565571
1.570724934665874
1.570795
0.00007139212902257958

tolerance = 0.00000001:
-0.000001326803844565571
183.5349266542149
1.570795
0.24824358078800488

[Martin Sjölund]

This ticket was not closed for 1.9.1, which has now been released. It was batch modified for milestone 1.9.2 (but maybe an empty milestone was more appropriate; feel free to change it).

[Martin Sjölund]

Milestone changed to 1.9.3 since 1.9.2 was released.

[Martin Sjölund]

Moved to new milestone 1.9.4

[Martin Sjölund]

Milestone pushed to 1.9.5

[Martin Sjölund]

Milestone renamed

[Martin Sjölund]

Ticket retargeted after milestone closed

[Martin Sjölund]

Milestone moved to 1.12.0 due to 1.11.0 already being released.

[Francesco Casella]

The milestone of this ticket has been reassigned to "Future".

If you think the issue is still valid and relevant for you, please select milestone 1.13.0 for back-end, code generation and run-time issues, or 2.0.0 for front-end issues.

If you are aware that the problem is no longer present, please select the milestone corresponding to the version of OMC you used to check that, and set the status to "worksforme".

In both cases, a short informative comment would be welcome.